1. Field of the Invention
The invention relates to a device and a method for image processing as well as an image processing computer program wherein multiple image areas are extracted from the basic image data according to image attributes (characters, photograph, graphics, etc.), then various image processes are applied to the image areas, and finally the image areas are synthesized to form image data for output.
2. Description of Related Art
Image data obtained by scanning a document with a scanner often has a large volume so that it may be unsuitable for storage or transmission/reception without being treated by a certain process. Therefore, it is often treated with a special imaging process such as compression depending on the type of image data. However, a problem arises when image data consists of a mixture of text image areas, graphic image areas and photographic image areas. More specifically, if irreversible compression suitable for photographic image areas is applied to the image data entirety, the volume of the image data reduces but it will be difficult to read texts. On the other hand, if compression suitable for the text image areas is applied to the image data entirety, a sufficient compression rate will not be achieved. In order to solve this problem, image processing devices have been used wherein text image areas, graphic image areas and photographic image areas are extracted separately, a compression process suitable for the particular area is applied to each area, and finally all the areas are synthesized to produce a document file. Such an image processing device enables us to reduce the file size while maintaining the image quality.
In graphic image areas, in particular, transformation of image data such as bitmap data into vector data is a widely used technique. Also known is a technique in transforming image data such as bitmap data into vector data by first dividing the image data into line areas, unfilled closed areas, and filled closed areas, and then treating each area separately.
However, the above image processing technique of the prior art, wherein a file is produced by synthesizing line areas, unfilled closed areas and filled closed areas, can cause a case where a filled closed area being laid over line areas and unfilled closed areas. Consequently, it causes a problem of not being able to reproduce the original image as the image data of the line areas and unfilled closed areas are hidden by the image data of the filled closed area.